BEHAVIOUR OF THE AMAZON DOLPHIN 



67 



Steinhart Aquarium in San Francisco, California. 



The director of the aquarium, Dr. Earl S. Herald allowed me to go to the upper 

 pools which are normally closed to the public. Here, two Inias are kept, one aince 

 1965 (Herald and Dempser 1965). The animais (fig. 18) are médium sized and 

 grey, the same as the animais in the Los Angeles aquarium. One of the animais 

 is quite tame and learns much more quickly than the other. If a 6 inches ring 

 weighted with lead is thrown into the water, the animal will retrieve it holding it 

 on the end of its beak. The pool is indoors and is rectangular approximately 5 

 meters by 3. The water is about 80 C F. The animais often stretch their heads out 

 of the water and can also stand on their tails with their heads out of the water. 

 Thèse Inias, like those in the Marineland of the Pacific, were caught in the Upper 

 Amazon (Iquitos, Peru) and transported by air to the United States. 



Discussion 



Detailed investigations on the ecology of In ia geoffrensis have not yet been 

 made and it would be interesting to make systematic investigations on the différent 

 biotops of the enormous Amazon basin. Almost no comparative parasitological 

 and haematological investigations have been made. The same is true of the food 

 and the stomach contents of the Inia. Intra and interspecific patterns of behaviour 

 are little known. Layne (1954) stated that Inia and Sota/ia fluviatilis inhabit the 

 same areas in Leticia (Upper Amazon, Peru). Promiscuity between species has 

 been seen by dolphins in the open sea, e.g. Stenella styx and Delphinus delphis, 

 Twsiops truncatus and Globicephala nielaena in the western Mediterranean 

 (Pilleri and Knuckey 1968). I did not see any Soialia in the Ibaré and Mamoré 

 rivers and the local hunters and fishermen said that they had never seen any other 

 dolphin than the Inia. 



a) Ranges 



The problem of a certain range for the Inia has not yet been mentioned in 

 the literature. I am of the opinion, following my observations, that the animais, 

 at least in narrow rivers such as the Ibaré, inhabit a certain territory. From Puerto 

 Almacén, up or down stream, the animais, isolated or in pairs but seldom three 

 animais together, are always seen at definite intervais from one another, and always 

 in the same place. The buffeos are usually found where the river is wider which 

 means a slower current. The river forms a sort of lake with deep clear water. The 

 Inia seems to be so bound to its range that even animais wounded with the 

 rifle can be seen the following day in the same area. I visited the Beni district in 

 February and I realise how important it is to compare the conditions during other 

 seasons. According to the farmers in Trinidad and the neighbouring areas, the 



